The former “Hills” reality star and the “Dancing with the Stars” pro were only dating casually but Conrad has decided to call it quits.

An insider tattled to Life & Style magazine, stating, “The relationship reached its peak. It was always casual. She had fun with Derek – he used to send her cute texts and sing to her – but she always kept her options open.”

Another pal believes Derek was a rebound relationship for Lauren after splitting from her boyfriend of three years, Kyle Howard, in June.

The insider added: “This was a rebound that wasn’t going to last. Derek never thought it would either.”